A Study On Parameters For Estrus Detection Based On Activity Record And Subclinical Mastitis Diagnosis Based On Milk Conductivity In Lactating Cows

This paper included two parts. In the first study, through analyzing the changes of activity, the ideal method to judge estrus by activity was found. The method can provide theoretical guidance to dairy production, and improve recognition rate of estrus. The second study investigated the relationship between EC and SCC. Then the optimum parameters of the equation were determined.The results indicated that dairy farm, season and region had effect on the amount of activity. For the high temperature in summer, the activity of cows decreased in Shandong. While in Mongolia, the activity of cow also decreased because of the low temperature in winter. Through analysis on the data of the three dairy farms in Mongolia, Beijing and Shandong, it was found that the activity gradually decreased from north to south, and the difference was significant. (P<0.001) The activity of cow in heat or not in heat decreased significantly as yield increased. (P<0.001) For cows in recessive estrus, change of activity is not significant. But yield and time in the ground decreased, which can be used to diagnose cow in recessive estrus. The amount of activity decreased significantly with increasing parity. (P<0.001) For one estrous cycle, activity increased in days before, after and in estrous, and it had no change in other days. Compared with other days, activity in one day before estrous increased by twenty paces, that in estrous increased by 370 paces, and that after estrous increased by 70 paces. The method that subtract activity before the day from activity in one day, then compared with 128 paces, can be used to judge cow in heat. The detective rate was above 90%, and erroneous rate was below 3.7%.In second study, 1200 lactating cows were selected from LUBAO, JINLAN, JIABAO XIANGHE and JIERUI dairy farms. The study investigated the effect of dairy, region, parity and lactation period on conductivity and parity, and then derived the equation of conductivity and SCC. It can be used to diagnose non-clinical mastitis.The results of the study were: the conductivity increased as increasing parity; (P<0.001) the SCC decreased in different lactation stages; (P<0.001) the change of conductivity was not significant; (P=0.54) For parturition cows, difference between SCC of the first ten days and that of other days was not significant after parturition. (P<0.001) SCC of the first ten days after parturition increased significantly, and then returned to the normal level within one month. SCC of back udder was significantly higher than that of front udder. (P<0.001) SCC of left udder was significantly higher than that of right udder. (P<0.001) The equation of conductivity and SCC was found in every dairy farm. The result showed that correlations between conductivity and SCC were different in the four dairy farms, and values of R2 were 0.9257, 0.8206, 0.8961, 0.9249. The R2 of the total equation was 0.6203. When SCC was more than 20 hundred thousand, the accordant rate of the total equation and the fact was 75%, while the SCC was more than 50 thousand, the accordant rate was 70%.